The clinical utilization of a pointed hollow needle mounted inside a flexible catheter tube may be utilized in the medical art for the introduction of a catheter. In such a medical instrument, the catheter tube is positioned tightly around the needle in such a way as to allow the needle to slide and telescope along the length of the catheter tube. Before use, the tip of the needle is protruding slightly through the opening of the catheter tube to allow facile penetration through the skin. Upon puncturing of the skin and introduction of the needle, the distal end of the catheter tube is simultaneously brought into place inside the desired target body cavity of the patient, such as the inside of a blood vessel, for example a vein. The needle has then done its duty in assisting the introduction of the catheter and is withdrawn by being pulled backwards through the catheter. Upon release of the needle, the catheter is set in its intended working mode extending over a lengthier period of time and including, for example, periodical administration or infusion of fluids or medications in liquid form, the collection of blood samples and the like.
An unprotected released needle constitutes, however, a serious health hazard due to the fact that it may be contaminated with e.g. infectious agents originating from the patient's blood or other body fluids, in combination with the needle tip's inherent ability to easily penetrate skin. Hence, the medical personnel who are handling the released needle may acquire the corresponding disease, e.g. HIV or hepatitis, if by accident contacting it with their skin. In order to circumvent or alleviate the health hazards associated with such a released needle amongst other things, there has been much effort devoted to the development of various kinds of needle tip protectors with a special focus on automatic variants of a type which may be referred to as being “foolproof”.
EP 1 003 588. discloses a safety IV catheter comprising a resilient spring clip normally positioned in the catheter hub. The needle of the safety IV catheter passes through a hole in the spring clip which allows axial movement of the needle. When the needle is in the forward position, i.e. when the safety IV catheter is ready for use, the presence of the needle forces parts of the spring clip into a position where these parts locks to the inside of the catheter hub, whereby movement of the spring clip relative the catheter hub is prevented. As the needle is withdrawn to a point where the tip passes these parts, the spring clip snaps into a position in which it is blocking access to the to the tip of the needle. Simultaneously, the part of the spring clip that previously locked to the inside of the catheter hub snap out of this position, whereby movement of the spring clip relative the catheter hub may occur. As the needle is further withdrawn, means are provided, e.g. a slot or a crimp on the needle, to lock the spring clip to the needle, whereby the spring clip is ejected from the catheter hub together with, and positioned on, the needle.
For various reasons, including e.g. practical, economical and technical reasons, the above described spring clips, and similar marketed variants, are today made of metal and catheter hubs of a plastic material. Disadvantages of the combination of these materials in this application include the release of e.g. microscopic plastic chips and metallic particles by the scraping of the metal spring clip against the inside of the plastic catheter hub when the former is ejected from the latter upon withdrawal of the needle. These chips and particles may easily be flushed into the bloodstream of a patient upon normal use of the corresponding catheter, and thus represent a serious health hazard to the same. This is especially true when the spring clip needs to pass beyond a bulge or something similar within the cavity of the catheter hub, onto which the metal spring clip should be brought into retained position until being released when the needle tip passes the distal part of the metal spring clip. Another disadvantage of the spring clip of this and similar safety IV catheters is the scraping vibration generated as the needle slides through and on the spring clip as it is withdrawn. This scraping vibration, which is due to metal sliding over metal and which can be clearly heard and felt, is highly uncomfortable and worrisome to the patient, who already is in an uncomfortable and exposed situation and may be very anxious.
Hence, an improved device for automatic shielding of the needle tip of a needle after its employment for introduction of a catheter tube is desired.